394 The Arteriole Recte of the Mammalian Kidney 
adding 0.3 to 0.5 grms. of the alkanin rubbed up in 20 ce. of acetone to 80 ce. 
of the stock solution, thoroughly mixed by stirring in a mortar and then 
filtered through absorbent cotton with the aid of a Chapman suction pump. 
For purposes of injection, I have made. use of compressed air, obtained by 
connecting a water tank with the laboratory water pipe. The tank is pro- 
vided with a pressure gauge, from which the pressure obtained is read. The 
pressure is conveyed to the table by means of a gas-pipe, provided with a stop- 
cock. The injection mass is placed in a large glass tube with 3 cm. lumen and 
about 20 em. long, held upright by clamping the same to a support. The upper 
end of the tube is provided with a perforated rubber cork, which can be 
clamped in tightly. A rubber tube leads from the end of the pipe bringing the 
compressed air to the table to a short glass tube fastened in the rubber cork, 
by means of which the pressure is conveyed to the injection mass. To the 
lower end of the glass tube, which tapers, is attached a rubber tube, provided 
with a clamp, by means of which connection may be made with the cannuia. 
The simplicity of this apparatus commends itself. It is shown in Fig. 1. 
As is usual in injections, better results are obtained by injecting a limited 
area, that is directly through the blood-vessel supplying the organ to be 
studied. It has not been found necessary to wash out the blood-vessels be- 
fore injecting. The animal is bled as freely as possible by severing the neck- 
vessels before death. The administration of amyl nitrite does not appear to 
influence materially the completeness of the injection. The injection is to 
be made soon after the death of the animal. The cannula is first filled with 
normal salt, and the salt solution renewed by means of a pipette until it re- 
mains clear in the cannula. It is then replaced with acetone, which is like- 
wise renewed several times to dehydrate the interior of the cannula. If the 
area to be injected is very small, a portion of the acetone is withdrawn from 
the cannula and this is filled with the injection mass. Better results are ob- 
tained by using relatively high pressure. In injecting the renal arteries of 
the dog, cat, and rabbit, a pressure of 20 to 25 pounds, as registered by the 
gauge connected with the tank, gave the best injection; for smaller animals, 
12 to 15 pounds. Better results are also obtained if the full pressure to be 
used is thrown onto the mass as quickly as possible. The pressure is main: 
tained for five to ten minutes. Before removing the cannula from the vessel, 
the vessel should be tied distal to the cannula, so as to avoid a back flow. A 
75 per cent solution of hydrochloric acid (sp. gr. 1.20) is used for macerating 
the parts to be removed. The entire organ may be placed in this macerating 
fluid, or, as it is often desirable to study a corrosion in small pieces, the or- 
gan may be cut into segments as desired and these placed into the macerat- 
ing fluid. The injected tissue may be placed into the macerating fluid 10 to 
20 minutes after the completion of the injection; there is no advantage in 
‘waiting 12 to 24 hours, as recommended by Krassuskaja. Pieces with one 
diameter not more than 1 cm. are thoroughly macerated in 18 to 24 hours. 
The macerated pieces are then transferred to a large dish of water and the 
softened tissues removed by playing water against them with a dropper pro- 
vided with a rubber bulb. It is not advisaple to use a stream of water with 
considerable force, as the delicate parts of the corrosion are likely to be 
injured. After the corrosion has been thoroughly cleaned, it may be allowed 
